junction box underground

[Robbox]

I need to extend solid core cable that runs in 25mm conduit, but box must be under some paving slabs. Would any IP68 box be suitable along with conduit fittings?

 

[Robbox]

I should also explain, that the underground cable comes from our conservatory. The conservatory was built after the house and the downstairs ring main has been extended to put sockets in the conservatory.
The extension of the original ring main comes into a fused switch initially.
The fused switch operates some ceiling lights and the incoming ring main cable uses the L & N connectors to make the bridge to the conservatory sockets and the outside spur to a shed, which has it's own CU unit.
Uncoupling the conservatory side, makes the outside spur safe but also makes all the sockets unpowered.
Couple of odd questions related to all this.
One of the sockets only has one cable going in, so I must assume it's a spur of one of the others.
There is no visible spur cable to the shed, so I have to assume that when the conservatory was built, a junction box was installed somewhere to make the shed spur. Would that be normal practice? It seems odd that the shed spur was not installed in such a way as to disconnect it without affecting the sockets.

 

[Adam_151]

Don't take this the wrong way, but it really sounds like you need an electrician on site to work out what is going on and sort things out in a safe an compliant manner.

Twin and earth cables should not be outside, let alone underground, any joint box you put under ground is going to let water in and cause problems, cable underground are generally jointed with resin filled joints but these arn't suited to twin and earth cable (because this shouldnt be found underground)

It sounds like there is a consumer unit spured off the ring, which again is wrong and again points to this all being a bit of lash up...

 

[Robbox]

Thanks. It was built some years ago (all cables are white, with red and black L/N) so that must date it somewhat. I too was surprised to see non-armoured cable in just a PVC conduit. I cannot imagine the electrics were not done by a professional, but perhaps regs were less strict a few years back.
I will leave this for when we renovate and have an electrician on site.

 

[securespark]

I had this issue with one of my Mum's outdoor lights (not installed by me).

https://www.diynot.com/diy/threads/best-of-a-bad-job.399851/#post-3080861

 

[ban-all-sheds]

I cannot imagine the electrics were not done by a professional, but perhaps regs were less strict a few years back.

I can, and no, they weren't WRT the things you appear to have wrong.

 

[ericmark]

It sounds as if the whole supply is protected by a 13A fuse, why you would have a consumer unit I don't know, seems over kill if all fed from 13A fuse. But to extend metal conduit is not easy, and also not easy to keep water proof, plastic is easy enough to extend but in both cases whole idea of conduit is you can draw in new cables, so I would not attempt to join them I would use new. It does not sound like a professional job, OK maybe the guy had a spare consumer unit knocking around, but if supplying from 13A fuse in a fused connection unit, then I would use a second FCU with switch to fuse down further for lights, not a consumer unit.